Peripheral venous catheterization is a routine everyday component of emergency medical practice. The normal human anatomy offers many potential sites for catheterization (Fig, 17.-1 and Fig 17-2). The arm veins are associated with an increased risk of phlebitis and are often technically more difficult to access than leg veins. The cephalic vein, in both the forearm and the upper arm, is large, constant, and straight; easily catheterized, it is the time-honored choice for peripheral access in both adults and children. The superficial radial vein at the wrist is well developed in adults, though it is difficult to locate in a small child. Veins of the hand are usually accessible even in obese persons but are short, tortuous, and difficult to stabilize. Veins in the antecubital fossa are excellent in emergency situations, but an armboard is necessary to prevent catheter kinking or dislodgement with movement. This is a relatively uncomfortable position for patients if access is required beyond a few hours. The large basilic vein in the upper arm is usually not visible, but with practice it can be catheterized by palpating the brachial artery and searching "blindly" for the medially placed vein. Puncture of the brachial artery is common but rarely of clinical significance if care is taken to prevent hemorrhage or hematoma formation; transitory paresthesias may also occur.
Veins in the legs often require cutdown for catheter placement. The superficial saphenous vein at the ankle is large, constant, and easy to isolate and cannulate. The proximal great saphenous vein in the thigh may be found reliably 5 cm below the inguinal ligament at the junction of the medial and middle third of the thigh in the supine patient. The deep femoral vein is accessible percutaneously, just medial to the femoral artery ( Fig 17-2). In the pulseless patient, the landmark is the junction of the medial and middle third of the inguinal ligament. From the great saphenous and deep femoral veins, advancement of catheters into the right atrium for the measurement of central venous pressure is possible.
Peripheral venous catheterization should not be attempted distally in an extremity involved by cellulitis, burns, or serious injury or when drainage occurs to an area that has sustained an acute serious injury (e.g., the right arm in the presence of a gunshot wound to the right chest). In such situations, the proximal veins may not be patent. Catheterization of arms in the presence of an indwelling fistula or serious neck trauma should also be avoided. Hyperosmolar fluids and agents known to cause chemical phlebitis or sclerosis of peripheral veins should not be infused through such veins.
Internal jugular, subclavian, or femoral vein catheterization is performed when peripheral access is impossible or when the measurement of central venous pressure is desired. The external jugular vein can provide reliable access in both adults and children. Although this vein is readily distended by the Valsalva or Trendelenburg maneuvers, scant subcutaneous support can make it difficult to catheterize. Access to central veins without the risk that attends direct internal jugular and subclavian puncture is a major advantage. In young children, intraosseous infusion provides rapid and reliable access in emergencies. A bone marrow or intraosseous infusion needle placed in the proximal, distal tibial, or distal femoral bone marrow can provide emergency access.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.